Apparatus for metallizing articles



Oct. 9, 1951 J. A. SARGROVE 2,570,600

APPARATUS FOR METALLIZING ARTICLES Filed Feb. 13, 1948 2 Sheets-Sheet lPROPANE OXYGEN ACTUAT E fix 5.].

. Inventor: aw w w,

Attorneys.

1951 J. A. SARGROVE 2,570,600

APPARATUS FOR METALLIZING ARTICLES Filed Feb. 15, 1948 2 Sheets-Sheet 236 g i6 m w W/QQ 1 G mm g I O Q a fatented ct. 1951 APPARATUS FORMETALLIZING ARTICLES John Adolph Sargrove, Shepperton-on-Thames,

England, assignor of one-half to Sargrove Electronics Limited, TolworthlEngl and, a British Application February 13, 1948, Serial No. 8,042 InGreat Britain February 19,1947

13 Claims. 1

Thisiinvention relates .to apparatus for met-' allizing articles.

In\my:co-pending U. 5; application, Serial No. 549,770; filed .August16, 1944, now Patent No. 2,474,988, there is disclosed a method ofproduce ing radio and kindred. apparatus which involves the production,for exampleby a moulding process,-of van: insulating panelin which areformed groovesand depressions .of particular shape; metal: is :thendeposited upon the panel and in the groovesand depressions the excess.metal on the surface :of the panel being subsequently .re-. moved1to-leave-;formed upon thepanel "some or all orthe components of theapparatus together.

processshould-be started andstopped only when one; Ofiiihfi; panels .isbeing handled in order that thetmaterial used inneach stage of theprocess isanot unnecessarily consumed.

With this object of automaticity in .view,v it is convenient to effectthe metallising deposit. by meansgzof metallisingiguns =of; knownconstrue? tion to which is suppliedthe metal to be atom-1 isedgusuallyas wirepandl a supply'of .fuel and other: gases for the production, ofheat, gas pressure andwelocity necessary for .atomising and.

spraying the metal, In the automatic operation Of-:-S\1Gh metallisingguns, .it. is thus necessary to control automatically thesupply of thegases andv oi, the metal; to ;be atomised, and to effect ignicnzo the ae In -the. operation-ofsmetallising,guns it is al-p waysa matteroflrdifilculty-to start :the guns sp iflyingwproperly, to the extentthat hand oporation-pf;the ,guns--,requires a high degreepf skill and,so ,faryas we ,arezaware, automatic starting has neverbeenrsatisfactorily. carried ut i pract e. hehreasonsafor; thisv aremany nxzl he. first placetheegases which are used to. providetheeal-oflfic yalue ofthegas mixture at therrgun 3 nozzle; are not:capable of. being. read-2 ily ignited in working, conditions.-Propaneand oxygen :are'frequently used for generating the necessaryheat, with compressed air for producing the blast for directingthemolten metal, which is fed as a wire into the flame.

Correct flame conditions, diiiicult as they are toootain, are nothowever suflicient to ensure correct-gun operation; correct wirefeed isalso. important since the melting of the wire accounts for. "a;substantial proportion. of .the heat 'consumed. If for any reason thewire .fails. to feed into. the gun, the gun. nozzle-Will overheat andmay eventually damagesthe gun. At the same timeiit is clearly wastefulfor the wire to be fed too. ,rapidlyin advance ofthe commencement of thegun operation.

Acccrdingtoone featureof the present inventicntherefore .we provide.means whereby-the wire-reed in-ia metallising gun canbe controlled,and-.accordingtopthe invention there is provided a Wire.feedmechanismwhich is controlled by. an air-operated clutch, from thesame air supply aspthatsupplied to the gun for. producing the blast fromthe nozzle. It will be realised that whilezthisieature is of particularimportance inanuautomatic apparatus, it is also applicable tomanuallyoperable guns.

Inafully automatic metallising apparatus according to the presentinvention means are providedf'or starting the. metallising processautomaticallyon the perception of anarticle to be metallised and forstopping the metallising when suchvartiole haspassed themetallisingstation orafter a predetermined .time,-and means arealsoprovided forystopping the process if there issainexcessive orinsufficient supply of the. metal being. atomised; or if any of :thegas. or other supplies is not present in suflicient quantity orpressure:

To secure fully automatic and economic operation ofwanwapparat-us it-isnecessary to make provisionnnot only forstarting the apparatusautomatically; but also for stoppingit' in the eventof-faults orabnormal operation. Automati'c' operation of any apparatus is notjustified if the production results in any excessive num-- ber of rejectarticles, and it is therefore necessary'to' ensure that the apparatuswill be stopped if-anythirig occurs which would resultin'a defectivepanel. For example with metallising apparatusthe apparatus must-stop ifthe gun'flame should be blown-out, or if any one ormore-of-the gasessupplied to the gun should fail, which would result in the metal notbeing-melted and s rayed.

According to a further feature of the present invention means areprovided whereby, in the event of the wire being fed from the gunwithout being melted and sprayed the unmelted wire makes contact with aconducting member, and the making of an electrical connection is used toinitiate corrective action, in this case stopping the apparatus.

Although this arrangement is simple and can be easily arrangedupon thespraying apparatus, the making of the contact will be an indication ofseveral abnormal conditions. Thus, the wire will be fed unmelted, andthe contact made, if there is a failure in the supply of any one or morethan one of the three gases fed to the gun, if the flame does not igniteproperly, or if the flame is extinguished, or if the wire should besupplied at excessive speed. In this way there can in fact be given bythis arrangement in a very simple way warning of the occurrence ofnearly all abnormal conditions of the spraying apparatus likely to causethe production of reject panels, with the exception of underfeeding orstoppage of the wire to be metallised.

According to a further feature of the invention, wire underfeed,including complete failure of the wire to feed, is indicated byarranging that the wire is passed over a pulley, upon rotation of whicha pair of contacts are momentarily closed at intervals as the pulleyrotates,

and means are provided to stop the apparatus if closure of thesecontacts is not effected within predetermined time intervals.

One embodiment of the invention will now be described with reference tothe accompanying drawings. In these drawings:

Figure 1 is a diagram showing the general arrangement of a metallisingstage such as may be adopted as one stage of a process for themanufacture of electrical apparatus in accordance with my aforesaidco-pending application.

Figure 2 is an electrical circuit diagram of the arrangement of Figure1, showing in particular the control unit therein.

The apparatus for carrying out this process comprises a series ofcubicles through which the articles to be treated are conveyed by meansof a suitable multi-section conveyor ID, and after initial treatment incertain of such cubicles by grit blasting and cleaning, the articles arepresented to the metallising cubicle ll, shown in Figure 1.

As the panel l2 or other article approaches or enters this metallisingcubicle II, it initiates the operation of the metallising apparatus;this may be effected by means of a presence detector 13 such as amechanical latch switch or trolley switch, or a light source and acontrol photocell. The presence detector i3 is coupled over a controlline i l to a main control unit l5. This unit, which is shown in moredetail in Figure 2 and will be described with reference to that figurehereinafter, is arranged to be responsive to a number of supervisory orsensing devices which are connected to input terminals Sense to controlcertain operations from output terminals Actuate.

The first stage in starting the operation of the apparatus is theignition of the flame from the metallising gun l6.

Preferably metallising guns are arranged on opposite sides of theconveyor through the cubicle I! and may consist of batteries of guns;these batteries may be arranged in the manner disclosed in another of myco-pending applications Ser. No. 10,702, filed February 25, 1948.

To avoid waste of sprayed metal it is desirable that the metallisingguns should be ignited and operated only when the metallising of a panelis being carried out, and unit 15 is therefore arranged automatically toignite the gun when a panel is presented to the metallising apparatus,and to permit the spraying process to continue for a time sufficient forone panel to be sprayed and then to stop the spraying process. Ifhowever a further panel is presented to the apparatus, the spraying willcontinue for a further period, and so on.

The control unit is arranged to ignite the main flame from the gun bymeans of a primary jet; over a control line I! the unit energises anormally closed, electromagnetically operated valve 18, which therebypermits a fuel gas, such as towns gas, of a more easily ignitable naturethan the gas supplied to metallising gun Hi to be fed to a pilot burnerl9. Over a control line 20 the control unit I5 operates a sparking plug2| of the usual type, and thereby ignites the primary jet. If there isused a battery of guns 16 arranged one above the other in each battery,it may be desirable to provide an additional burner, similar to burnerIQ, for each gun, the additional burners being directed horizontally butarranged substantially one above the other and the primary burnerdirectly vertically upward and arranged below the lowest additionalburner. The primary burner then ignites the secondary burners (which arenot provided with sparking plug igniters), which are in turn arranged toignite the main guns. It is difficult to ignite a series of guns fromthe one primary jet as the lowermost gun tends to blow the ignitingflame from the upper uns.

The control unit also controls the supply to the gun l6 of the necessarygases; over control line 22 valve 23 is operated to supply the fuel gas,such as propane, to the gun, and over control line 24 valve 25 isoperated to supply oxygen to the gun. Over control line 26, valve 21 isoperated to feed compressed air to the gun, and with sequence ofoperation the necessary flame is produced at the gun nozzle or nozzles.

With this operation, however, it is most important that the wire shouldbe fed to the gun; as mentioned above the guns can be damaged if theflame continues without wire being fed. According to a feature of theinvention, this wire feed is eifected by the application of the airpressure to the gun.

The wire 28 is fed from a drum, not shown, over the face of a driveroller 29 driven by a motor 30, which is under the control of the unit15 over control line 3|. The engagement of the wire 28 with the roller29 is however inadequate to cause the wire to advance, but the necessaryfriction is obtained by means of a backing roller 32; this latter rolleris movable by means of air pressure device, shown diagrammatically inFigure l, as comprising a cylinder 33 and piston 34. The cylinder issupplied from the compressed air line controlled by valve 21. Thus, assoon as air is admitted to the gun by valve 21, the backing roller movestoward the roller 29; the wire is thereby fed to the gun simultaneouslywith the starting of the gun flame, which is very desirable.

In practice, the rollers 29 and 32 and the air operating means for thelatter roller are structurally combined with the gun assembly l6, andthe cylinder 33 may be replaced by a diaphragm or equivaIent airoperated device.

and rollers 19,32, the wiref'which-ispassed once of the'load of drawingthe wii e from the'drum.

'ing of the articles. 7 zontally past the gun'orguns the spray' "can besulting motion of the' gun willhea simple harand which is illustratedmore completely in my aforesaid co-pencling application Ser.No.- 10,702,

'The piston is double-acting, and air is admitted 'contro1'- of the'control unit tosecu're extremely tion' initiated by the presence "49driving an exhaust fa Thiscauses'a flowof v sprayed assisting the'cooling of thepanel, and draws on combustion 'p oductsrrom' thecubicle.

defective mans-sing, m n o'fftl'ie panels. Thus'-'-'ifa meta lis ing g n1811013 'correctly ignited, if 'the supply oi any one or 75 YIhe when isdrawn froms 'd'i'um whic must be of large capacity inord'er that theprocess mayfrun for aslong periods as possible without "stopping forre-loading. "A 'srvoin'echanism" is therefore included to assi's't theunreeling of the drum. This'comp'ris'esa' capstan pulley 35, driven bymotor 36, under the control of the unit *over c'ontrol lihe '3'l. Solong as there is any slack in the wire b'etween pulley round the pulley,slipsybutwhe'n the sIack is 10 taken up by thecommencement "of pulleys'29 "and 32 to drive the wire is-tightened' upon "the pulley and motor36 then takesthe-major'part For the metallising'of Inanyart'i'cles it islikely that the spread of the molten' 'spra'y from the guns isinsufiicient-to produce'- uniformspray- As the articles move horimadeuniform by moving theconvey'onat strictly 20 uniform speed and theispeedmay-"be controlled monic motion, and thethlckness' of deposit willincrease at the limits-of travel. A's'implemeans for rocking the gun insuchnianner that its motion is linear; i; e. uniformwith-respect totime,

is'shown diagrammatically in Figure land comprises a cylinder- 38 withinwhich is a piston 39 mechanically coupled to the' g'un'by'a'rod 40.

tonne or other of theends of the cylinder through air-valves 4|,dz-under 'the control of unit I5 over control lines 43, 44 respectively.Therod e0 'is 'also arranged to operatea pair of limit switches 45,46whichare coupled-overthe 50 control line 47 to the sense input of thecontrol unit. As each limit of travel of 'thepiston is reached, oneoroth'er ofthe 'limit switches is operated and the valves fl or- JZrnoVed' -un'der rapid reversal of the-movemntof tne E am suitable'po-int' in 5 the sequence of operatector; theme-n. trol unit I 5, overcontrol line starts-a motor Difdr' meantime I I panel being seatsmidescend nga parat samends ther panelsa're vice-l3. 7

ri er the satisfactory oper' t" of the apparatus itisnecessarfto"EnSui'e iIiQt hG ED? stopped if any conditionsarisewhichmoreof the gases to the "gun should not-occur, ii the flame should "beextinguished fortuitously, or' if the wire feedshould fall belowtherequisite amount, or if the main supply of electric-power shouldfail; in the event of any one or more of these contingencies arising theapparatus must be stopped. Moreover if, say, the-power supply should' becut off and then restored, the apparatus must not be left in a dangerouscondition or restored to a dangerous condition.

As with all automatic machinery it is noteconomic to provide forcontingencies ofve'ry low probability of occurrence sincewith good"practice the machine will be operated with periodic, but notcontinuous, skilled maintenance. Thus it is'no requirement for economicautomatic operation to protect the machine against mechanical breakagesor derangements since'a maintenance engineer can be expected toanticipate such breakages, or to repair them manually.

Notwithstanding this, however, the :prote'ctionof the machine as awhole." is a complex matter.

With one feature of the present invention, a particularly simplearrangement is adopted to give warnin of a number of possibledefectsbfthe apparatus.

If any of the gases suppliedwo the gun fails, or the flame isextinguished, the Wire will continue to feed from the gun and' willemerge as an unmelted wire from the nozzle. According to the inventionthe gun, which electrical contact with the wire to be 'melted isinsulated from a memberimmediately in'fro'nt of the gun and with whichthe'wire will contact if not melted. This member is convenientlyprovided by the frame of the cubicle itself; from which the gun or gunbattery is electrically-insulated. The completion of anelectricalcircuitbetween gun and cubicle is used over'contro1 line 5| to control one ofthe sense inputsof the unit I5, which thereuponeflects thedesiredcontrol operations.

Where the arrangement of the gun assemblies is as described in myco-pending application No. 10,702, the insulation of these assemblies issimply effected by mounting the rocking means for these assemblies insuitable insulating *bu'sh'es.

It-will be clear that it is necessaryalso to insulate the wire and thewire reels from el'ectrical contact with the main body of the cubicleand this is conveniently effected by providing for the wire in itspassage from the reel to -the guns guide pulleys over which thewirepasses and which are mounted so as to be insulated from the cubicle.If the reels for the vvire are of metal, it is necessary also for these'to"be'-insulated from the cubicle by means'of suitable insulatingwashers.

In order to check that suilicient wire'isbelng fed to the gun, We preferto make use o-f one of the u de pu eys f ex m le the-'e idepuue 52 and tarra e f r ins "5 c on h' p ey to operate in its rotation-a pair ofcontacts-53, motion of thepulley successively closing these contacts; asshown in my co-p-ending application Ser. No; 10,702, the contactmechanism'53is-so constructed that any stoppage of the pulley, even atthe moment of contact, is arranged to open the contacts. Over thecontrol line '54 the periodic closure of contacts'53 is --applidi-to-asense input of the control unit [5. w' ill 'be described below, thecontacts are employed on each closure to remove a normally prohibitivebias on the grid of a valve; if the contcts'are not i closed againwithin a given time the proe hibitive bias is restored, but on each'closure-"oi complete electrical apparatus.

7 the contacts the bias is again moved from the prohibitive value. Itwill be observed that this arrangement is self monitoring in that valvefailure, in which the anode current of the valve falls to zero, has theeiiect of stopping the apparatus.

To stop the metallising process should the electric supply fail Whilemetallising a panel all the gas supplies are controlled byelectromagnetic valves or" the type which close in the absence ofenergising current. Valves of the socalled motorised types which requireelectrical energy to efiect opening and closing are not suitable; it ispreferable to use valves of the type where closure is effected bygravity or spring return whilst electrical energy has to be applied allthe time the valve is open.

In Figure 2 of the accompanying drawing is shown by way of example onecircuit arrangement of a control unit such as 15. In this diagram thevarious control lines connected to the unit l are not drawn as extendedlines, but for convenience the diagram has been made more compact. Thediagram of Figure 2 therefore includes the electrical circuit of theunit proper, and includes as elements the various gas and other valves.

Before describing the arrangement of Figure 2, however, it is desirableto indicate the relation of this metallising stage with the associatedstages with which it forms a complete and au tomatic machine forproducing substantially Upon presentation of a moulded panel to themachine, the first stage of the machine, namely the grit blaster, isstarted and the succeeding stages are brought to a state of readiness toreceive the panel as it is presented to them.

As the panel proceeds through each stage of the machine it starts theprocessing in that stage, and after some or each of the stages theprocessed panel is tested. If the panel differs from a standard by morethan a tolerable amount, the relevant stage of the machine is adjustedii that is practicable; if not, the relevant stage and all the precedingstages are stopped, but the succeeding stages are not affected. Ifadjustment is made and still does not result in the production ofsatisfactory panels, the relevant stage will be stopped after, say,

.three panels have been produced with characteristics outside thepermitted tolerance. An alarm or indicator is also operated to call theattention of the maintenance engineer.

In the particular apparatus in which the arrangement of Figure 2 isintended to be incorporated, two metallising stages are incorporated;the arrangement of Figure 2 relates to the first st e- In thisarrangement, the operation is initiated by closure of contacts l3 of thepresence detector bearing that reference in Figure 1; for test purposesthere is provided a push button Start in parallel with these contacts.Closure of contacts l3 completes the circuit of a relay M/3 betweenearth and positive terminal of a +24 volt earthed-negative supply. Onoperation of the relay M/ 3 its contacts Ml close, and thereby completethe anode circuit of a valve Vi, of which the cathode is earthed, andthe anode is connected through contacts M: and a rela A/ 2 to a sourceof anode supply. The grid circuit of valve VI includes a grid resistorR| shunted by a condenser C and, under the control of changeovercontacts J I, t e grid is returned through a high value resistor R2either to the line 24- or to a line 24+ connected to the positiveterminal of an earthed-negative supply. The potential of the grid of thevalve VI is also controlled from the contacts 53 on pulley 52; thesecontacts are connected to the line 24+ and through the resistor R3 tothe grid of the valve. A condenser C4 is connected between the contactsand earth.

With the contacts JI in the position shown, there is placed upon thegrid of the valve VI a. substantial positive bias, so that upon closureof the contact Ml a large anode current flows in the valve and relay A/2 operates.

Relay M/3 when operated also closes contacts M2 which are included inthe cathode circuit of a second valve V2. The cathode of this valve isthereby connected to a point upon a potential divider formed byresistors R4, R5 across the anode supply, the cathode thereby beingconnected to a point of positive potential with respect to earth. Thegrid of valve V2 is connected to earth through three resistors R6, R1,R3 of which R8 is variable, but by a contact M3 of relay M/ 3 the ridcan be connected over a direct path through to the anode of the valvethrough resistor R5. With contacts M3 closed therefore the valveconducts, and the anode current in this condition is sufiicient tooperate a relay J /3 included in the anode circuit of the valve.

The initial operation of contacts l3, or the start button will bemomentary, and to prevent the relays A/2 and J/3 dropping out when thecontacts 13 open, contacts A/I of rela Al are arranged in parallel withcontacts MI to maintain the relay A/2, and contacts A2 are in parallelwith contacts M2. Contacts M3 are not shunted by any contacts of relayA/2.

The operation of relay J 3 as described above is employed to set inmotion a multi-bank stepping switch of usual construction having banksSMI to 3M8, each bank having 24 positions and one home position. Thedrive magnet SM of this switch is connected between the wiper arm of thebank SM! and earth, and contacts 1 to 21 of this bank are connected to24- and to the moving contact of changeover contacts J2 or the relay J/3. Contacts 22 to 24 are connected to one of the stationary contactsJ2, and the home contact 25 of the bank is connected to the otherstationary contact J2.

As soon as contact J2 chan e v r. the hom contact of bank SM! isconnected to the voltage line 24v and the wipers of all the steppingswitches s e rapi y o po iti 2.. a in Home 0 t e e u ce of st t ng he el s ng c s ta s pla e A so n posi on 1 s a ed. ba k S c m te the cir itof a r ay T/l c s t r i s e h. a 24-; h rela on erates and its contactsTl energize the 1am. magnetic valve [8 of Figure 1, and town gas is appt the p i a j t 9. Th s val e re= o e un osit on 2' o h s i ch s sreached,

At p s i n an s SM! an 5M re on te in a a lel o up l u ren t t e pr arywi ng o he i o de ice parallel contacts are used as a comparative largecurrent is equ re or t is purpo ehe gnition device continues to operateover positions 1 to 16 01 the swit hes.

At position 9, bank SM3 completes the circuit of a relay G/l, thecontacts GI of which energise the valve 23. and thereby feed propane orsimilar relay E/2 the contacts El, E 2I. ,oif which, in parv allel toincreasectheir current-carryingcapacity, supply powerto theexhaustermotor 49 and to, the motor 351 forthecapstan pulley 3 5.-,

At position l'lbanks SMZ and 5M4 stops l plying the ignition device 21,and bank;SM2,energizes relay 0/ I the contacts Q! of which supplypowertov valve 25 and cause oxygen to be fed, to the guns.

At position 21 and also at. position, 2 2c bank SM5 energizes relay 2/ Ithe contacts Z1 ofwhich. cause operation of valve 2! to applycompressedair to the guns and to cause the zinowi jeto feed; At position 2 1 asdescribed above, the town gas supply valve closes, and the steppingswitch comes torest on position 22, sincethe drive magnetis deenergizedon reaching contact 22 of bankslvll.

As soon as the switch; bank 5M6 reaches posi tion 9 and relay E/ 2operates, voltage is applied through contacts El andEZ am i throughcontacts Ql of a relay Q/2 to one or otheroi the valves or 42controlling the oscillation of the gun. The coil of the relay.Q/2, isconnected between earth and 24+, and includes contacts Oftljielimit Iswitches-45 and 46 in series, the contacts 46 being; shunted bycontacts-Q2 of the relay. Contacts 45 arenormally CIOSBdfiIld'fiI'Bjmomentarily opened at the limit of movement of the gun, while contacts46' are normally open and are momentarily closed at the otherlimiter-movement; As shown in the position of Figure 2 contacts and Q2are opened, and the relayQ/2 -is deenergized'; contacts QI are as'shown;and valve 4| is operated. Air is thereby admitted-totheupper side-ofpiston 39 which accordingly movesdownwardly until" it reaches thelower-limitof movement and switch contacts 46 are closed. Relay-Q/2 thenoperates, changing overcontacts Q! to energise" the valve 42 to reversethe directionofmovement of the piston 39. Contacts Q2 close, sothat therelay Q/2 remains operated after the limit switch contacts 46 areopened; The -piston moves to theother limit of movement; contacts-45 areopened; relay Q/ 2 drops out and the cycle of-movement is continued. Themetallising process should now be performed I satisfactorily.

It is necessary. tostop the apparatus after apredetermined timeinterval, representing the time taken to process one panel, and thisiseffected by means 10f a timer-delay resistance-condenser combinationassociated with the grid circuit of the valve V2. This gridcircuitincludes a. condenser C2which, when relay J 3-is-not operated isdischarged. through contacts J3vand a'resistor R9; Whena-panel ispresentedto the ap aratus, as d scr bed above. the r lays M- 3'and J 3operate, and in this condition the condenser C2 is connectedinparallel.with'-contacts-M3,= andthe' condenser terminals are thereforeat the same; potential When they trailing. edge. of the panel passesthepresence detector ,itscontacts I 3open, and re.-. lay M/3 isde-energized; relay A/2rremainsoperated and; the, anode? and cathodecircuits of valves -VI 1 andVZtare complete. Asasoonas the contacts M3open however the ShOlt: circuit is: removed from-the terminals:.-of thecondenser C2 1 and the condenser beginsito draw a;. charging: currentthrough relay- J 3iand=resistors R1; R8. As the voltage, on thecondenser increases so; they rid of the -va ve.. ccomes more-negativeand .the 7a.;

it ll anodecurrent decreasesithere are accompanying efiectsin that thegridcurrent decreases as the grid potential decreases, but the resultantis=thatafter a time. delay, adjustable by resistor RB, the anode currentof valve VI drops to a value where relayJ/B, is no longer, heldoperated;

When relay J flidrops out, contacts J2 change over andthe drive magnetvSMis energised over the contao,ts\ ,22 to 24 ofthe switch bank SMl, andall the switches return to the home position.

The oxygcn control valve 25 is released at po-.. sition 22,,and the fuelgas valve at 23- and theexhanst motorisde-energised at 22. In practice.it is Ioundto, be desirable to leave the metallisingguns with a shortlength of wire, about half-an-inch long, protruding from them, andmeansare, therefore provided for, maintaining thgpOWBli supply to. air valve2l-for a short ime aftellthe other s in lies are cut off. With thisobject there is p ded a valve V3,.which is sornewliat similar to ValveV2. in its opera.-. The cathode. of the valve isconnected to a poi ntoi; positive potential upon a potentialdividerformed by resistors R10,RH and they anode circuitof thevalve includes a relayP/Z.

The grid of the. valve is, returned to earth through resistOl i R12,R13, Rl4-of which the lastis.

adjustable. In. the normal condition there. is placedbetween gridandcathode of the valve a bias which is sufficient to. prohibit anodecurrent; the, relay P/Z. is therefore normally reea d When theswitchbankv SM8. passes over position 22, however, the resistor. RIZ.isconnected between grid andanodeof the valve, anode current flows andrelay P/2 operates. Contacts Pl oi tlii s relay cl ange-over and therebydisconnects acondenser cl from adischarge resistor and connects, itbetween anode, and. grid,

circuits of the valve; as, described in connection with valve V2,, thisarrangement sustains the anode current ofthevalve while the condenscrcharges up. w TherelayP/Zalso has con-, tactsP2 in parallel with thecontacts 2! of relay Z/i, so maintaining operation of air valve 21 and.thus feed of the. wire for. a. time deter-.

minahle by the, value, of the adjustable. resis tor Rl L Itisalsonecessary-to stop the. apparatus if and, stop the apparatus inthe'manner described,

above.

lf the oontaets fifi are periodically. cloS9d, however, aswhen the wireis feeding at the, correct speed, the contacts, periodically charge-acondenser C4hfrom-the line 24+ and this charged condenser is-connectedtothe-grid of valve VI throughresistors R3 and Ri. This condenseraugments the; charge on condenser Cl and thus delays the change of anodecurrent necessary,

ton-release relay. A/2-; if: the condenser is recharged-sufficientlyrapidly the. anodecurrent change, a is delayed indefinitely.

The apparatusrmustalsoflbe stopped if con-.

tact is made between the gun and its cubicle, presenting a short circuiton the control line as will occur if the wire is fed unmelted. For thispurpose a relay L/Z is provided normally energised through a resistorRIB from the line 24-, the relay contacts Ll controlling the anodesupply to the valves VI and V2. When contact is made across the line 5|a short circuit is placed on the winding of the relay L/Z, and the relayreleases contacts Ll opening and removing anode supply voltage to valvesVI and V3. Contacts L2 of this relay close when the relay releases, andcompletes the circuit of a pilot warning lamp PL. A stop push buttonStop is also provided, its contacts in shunt to the line 5|.

As thus described the arrangements of Figures l and 2- provide a fullyautomatic, selfrnonitoring metallising apparatus, which has been foundsatisfactory and reliable in operation. For the purpose of carrying outthe process of my co-pending application Ser. No. 549,770 however, it isdesirable that the metallising should be effected in two stages, and theequipments of Figures 1 and 2 are therefore largely duplicated, and areinterlocked so that if the first of the two stages should fail or becomedefective for any reason the second may continue to operate, whilst ifthe second should fail, both stages are stopped.

Moreover, three stages may be provided, the control units of which maybe interlocked so that any two stages may operate, the third stage beingbrought into service as soon as one of those two units becomesunserviceable.

I claim:

1. A metallising device including a spray gun to which metal is fed as awire for melting and ejection from the nozzle of the gun as a moltenmetallic spray, means for feeding wire in continuous form to said gun,means for su plying combustible gases to said gun and igniting the samefor melting the wire as it is fed to said gun. means for supply n presure g s to said gun for ejecting the molten metal from the gun nozzle,and means responsive to the projection of unmelted wire from the gunnozzle in the e ent of failure of the gun to melt the wire for haltingsaid wire feed and cutting oil said gases.

2. A metallising device according to claim 1,

wherein said wire is electrically conductive, said wire feed and gassupply rnens are electrically controlled and the said means for haltingthe wire feed and cutting o f the gases is con rolled by circuit meanscompleted throu h contact of the unmelted leading end of the wire with astationary contact member disposed in the path of the wire.

3. In a m tall zing spray un apparatus of the type utilizing acombustible gas having a high calorific value for melting the metal andcompressed air for spraying the molten metal from the gun, means forsupplying a readily ignitable gas to said gun, and means for ignitinglast said gas to form a primary flame for igniting said high calorificgas.

4. A metallizing spray gun apparatus as defined in claim 3 wherein saidprimary flame is established prior to admission of said high calorificgas and compressed air, and continued for a predetermined time.

5. Apparatus for the metallization of articles comprising a metallizingspray gun, a conveyor disposed to transport articles to be metallizedpast said spray gun, electro-actuated means, controlling admission of areadily ignitable gas to said'gun, second electro-actuated means forigniting said gas to form a primary flame, third electro-actuated meansfor controlling admission of a combustible gas to said gun having highcalorific value for melting the metal to be sprayed, fourthelectro-actuated means for controlling admission of compressed air tosaid gun for discharging the molten metal in a spray, anelectro-responsive presence detecting device disposed adjacent saidconveyor on the approach side to said spray gun and controlled by thearticle thereon for producing a presence signal upon approach of thearticle to said spray gun, a step switch mechanism controlling theoperating sequence of each of said electro-actuated means, and meansresponsive to said presence signal for initiating an operating cycle ofsaid step switch mechanism.

6. Apparatus for the metallization of articles comprising a spray gun,means for feeding metal in continuous wire form to said gun, means formelting and spraying from said gun the metal fed thereto, and controlmeans including a pair of contacts adapted to be actuated periodicallyat a rate proportional to the rate of feed of said wire to the gun forterminating operation of the latter upon a drop in the wire feed rate toa predetermined minimum value.

7. Apparatus for the metallization of articles as defined in claim 6wherein said wire is fed over a pulley having means thereon foractuating said contacts at a rate proportional to the pulley speed.

8. Apparatus for the metallization of articles comprising anelectro-controlled metallizing spray gun, a conveyor disposed totransport articles to be metallized past said spray gun, anelectro-responsive presence detecting device dis posed adjacent saidconveyor on the approach side to said spray gun and controlled by thearticle for producing a signal upon the approach of an article to saidspray gun, a thermionic valve, relay means connected in the anodecircult of said valve and which control operation of said spray gun,means controlled by said sig nal for changing the anode current of saidvalve from its initial value to a value suflicient to efiect operationof said relay means thereby initiating operating of said spray gun, andmeans for thereafter restoring the anode current of said valve to itsinitial value after a predetermined time interval to effect release ofsaid relay means thereby terminating operation of said spray gun.

9. Apparatus for the metallization of articles as defined in claim 8wherein said valve in the absence of an input signal is arranged withits anode circuit opened by contacts therein, and wherein, with saidcontacts closed, there is placed upon the grid of the valve a bias withrespect to the cathode sufiicient to prevent operation of said relaymeans, and wherein to permit operation of said relay, the grid of thevalve is connected over a direct current path including a second set ofcontacts and a resistor therein to a point of positive potential.

10. Apparatus for the metallization of articles as defined in claim 9wherein the grid of the valve is arranged to be connected via a resistorto the anode of the valve, and wherein said second set of contacts areadapted to be bridged by a condenser arranged to be charged up slowlyupon opening of said second set of contacts and thereby to reduce thegrid potential to a value to cause release of said relay means 11.Apparatus for the metallization of articles as defined in claim 9wherein the grid of said valve is arranged to be connected via aresistor to the anode of said valve, and wherein said second set ofcontacts are adapted to be bridged by a condenser of adjustable capacityarranged to be charged up slowly upon opening of said second set ofcontacts and thereby to reduce the grid" potential to a value to causerelease of said relay means.

12. Apparatus for the metallization of articles comprising anelectro-controlled metallizing spray gun of the continuous wire feedtype, a a conveyor disposed to transport articles to be metallized pastsaid spray gun, an electroresponsive presence detecting device disposedadjacent said conveyor on the approach side to said spray gun andcontrolled by the article for producing a signal upon the approach ofthe article to the spray gun, a thermionic valve, relay means connectedin the anode circuit of said valveand which controls operation of saidspray gun, means controlled by said signal for changing the anodecurrent of said valve fromits initial value to a value sufficient toactuate said relay means thereby initiating operation of said spray gun,a delay acting condenser-resistance network connected in the gridcircuit of said valveand effective upon said change in anode curre'ntitogradually restore the same to its initialvalue thereby effecting arelease of said relay means, and means including a set of contactsactuated at a rate proportional to the rate of feed of said wire formodifying the efiect of said condenser-resistance combination on saidanode current.

13. Apparatus for the metallization of articles comprising a metallizingspray gun, a conveyor disposed to transport articles to be metallizedpast said spray gun, a conduit for delivering a combustible gas to saidgun, valve means in said conduit controlling the flow of saidcombustible gas, means for feeding wire in continuous form to said gunfor melting of the leading end thereof by the heat produced bycombustion of said gas, a presence detecting device disposed adjacentsaid conveyor on the approach side to said spray gun and controlled bythe article to be metallized for actuating said gas valve to openposition for a predetermined period of time and effecting operation ofsaid wire feed means for a slightly longer period of time.

JOHN ADOLPH SARGROVE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,262,134 Stolle Apr. 9, 19182,271,442 Sanborn Jan. 27, 1942 2,281,169 Pattison Apr. 28, 19422,381,932 Shepard et a1. Aug. 4, 1945 2,434,176 Potthoff Jan. 6, 1948

